403
AWUS01 KWNH 141942
FFGMPD
PAZ000-MDZ000-VAZ000-NCZ000-DCZ000-WVZ000-OHZ000-150140-

Mesoscale Precipitation Discussion 0435
NWS Weather Prediction Center College Park MD
340 PM EDT Sat Jun 14 2025

Areas affected...Upper OH Valley...Central
Appalachians...Mid-Atlantic

Concerning...Heavy rainfall...Flash flooding likely

Valid 141940Z - 150140Z

SUMMARY...Scattered areas of flash flooding are expected to occur
this afternoon and into the evening as heavy showers and
thunderstorms develop and expand in coverage. Locally significant
urban flash flooding impacts will be possible.

DISCUSSION...The latest surface analysis shows a quasi-stationary
front draped across the Mid-Atlantic region and stretching back up
across the higher terrain of the central Appalachians and the
upper OH Valley. A substantial amount of moisture is in place
along this front with PWs in general across the region running
nearly 2 standard deviations above normal.

In fact, the 12Z RAOB data from KPIT and KIAD showed very moist
soundings with PWs of 1.79" and 2.01" respectively. Tall, skinny
CAPE profiles were noted as well, and thus the environment is
conducive for highly efficient rainfall processes that could yield
extreme rainfall rates as convection develops and expands in
coverage over the next several hours. The airmass along and
adjacent to the front continues to destabilize with the diurnal
heating cycle, and MLCAPE values have risen to as much as 1000 to
1500 J/kg on the warm side of the front across central WV and also
across central to southeast VA.

The increasingly concentrated axis of moisture and instability
along and near the front, along with areas of locally more focused
surface convergence should favor the regional development and
expansion of heavy showers and thunderstorms over the next several
hours. Some modest shear profiles and upper-jet aided
ascent/divergence over the region should also facilitate this
evolution with eventually broken clusters of convection
materializing.

Near-term convective development over the upper OH Valley and
central Appalachians is expected with the aid of the front and
also orographic ascent. However, by late this afternoon and this
evening, the front itself from the MD/WV Panhandles on down
through northern/central VA and eventually the Tidewater/Hampton
Roads area of southeast VA should become quite active with
convection impacting these areas.

Rainfall rates may reach 2 to 3 inches/hour with the stronger
storms given the moist/efficient environment that is in place, and
some localized storm totals of 3 to 5+ inches are going to be
possible given the relatively slow cell-motions that are expected.

A combination of urban sensitivities and moist antecedent
conditions in general will combine with the additional rainfall
potential to support a notable threat of flash flooding going into
the evening hours with at least scattered areas of flash flooding
likely. Locally significant urban flash flooding impacts will also
be possible if these heavier rains focus into the urban corridors.

Orrison

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...AKQ...CTP...GSP...LWX...PBZ...RAH...RLX...RNK...

ATTN...RFC...ALR...RHA...TIR...NWC...

LAT...LON   40847927 40557796 39957700 38917648 36987556
            36267629 36207854 35917986 35748123 36088172
            36988074 37918036 38638084 39678195 40568123